The present invention is in the field of seismic isolators. More specifically this invention relates to seismically restraining equipment which must also be vibrationally isolated.
Building codes in many areas require that certain types of equipment be seismically restrained. Newer codes are increasingly requiring equipment mounting to meet a very wide range of seismic forces. In the past, a 1 G rating would work almost anywhere. Now there are applications with requirements as high as 3–4 G's and others with requirements as low as about 0.25 G's. Seismic restraints which can handle the peak loads are overkill for applications having only minimum seismic requirements. A seismically restrained vibration isolating mount is desired wherein the vibration isolator could be sized separately from the seismic restraint such that effectiveness could be maximized while cost is minimized.
Seismic capacity is typically limited by the isolator anchorage capacity. A seismically restrained vibration isolating mount is desired wherein the seismic restraining contact point is moved closer to the mounting surface thus significantly reducing the tipping loads that can be generated in the restraint housing. U.S. Pat. No. 4,356,992 by Donald E. Benkert discloses an earthquake protected vibration isolator where the seismic restraining contact point has been moved closer to the mounting surface to reduce the loads on the anchorage points. However in Benkert the equipment sits on top of the isolator, and so would have to be moved to change the spring. Also in Benkert, a portion of the snubber covers the spring, and thus the snubber plate would also have to be removed to change the spring. It is desired to have a seismically restrained vibration isolating mount wherein the vibration isolating resilient element is easily accessible, adjustable, and replaceable.
Further, in Benkert and other known configurations, the equipment is resting on top of the resilient element, which in turn is resting on the mounting surface. A seismically restrained vibration isolating mount with a more stable mounting configuration is desired.